JP2002173246A - Belt driving device and electrophotographic apparatus provided with the same - Google Patents

Abstract

[PROBLEMS] To control the transfer conveyance belt 1 that conveys a recording sheet p to a plurality of image forming units A to D arranged along a conveyance span by controlling the torque of a detection ring 29 that rotates when the transfer conveyance belt 1 meanders. In an electrophotographic color printer in which the movable end 6a of the roller 6 is moved to the front side in the belt traveling direction to control the belt meandering, the control roller for the transfer conveyance belt 1 is not subjected to excessive restrictions on the belt layout. The meandering control function of No. 6 can be properly exhibited. SOLUTION: When a friction coefficient μ between a control roller 6 and a transfer conveyance belt 1 is μ = 0.3, a contact area S between the control rollers 6 and 1 is set to S ≧ 8250 mm ² .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt driving apparatus which controls a belt meandering by a control roller which guides and supports a belt, which conveys an object to be conveyed such as a recording sheet, while frictionally contacting the belt. The present invention relates to an electrophotographic apparatus, and particularly to a measure for appropriately exerting a meandering control function of a control roller.

[0002]

2. Description of the Related Art For example, in an electrophotographic color printer, as shown in FIG. 7, a transfer / transport belt d is runably wound between a plurality of rollers a to c. Image forming units A to D for a plurality of colors (four in the illustrated example) are arranged along a transport span formed between the predetermined rollers c and a. In each of the image forming sections A to D, the transfer conveyance belt d is pressed against the photosensitive drum e by the transfer roller f so that the photosensitive drum e
The upper toner image is sequentially transferred to the recording paper p on the transfer / conveyance belt d. E in the figure is a fixing unit for fixing the toner image on the recording paper p.

In such a color printer,
When the transfer conveyance belt d meanders, the position of the toner image is shifted in the belt width direction, and the image quality is degraded. As one of the measures, for example, a belt meandering control technique described in Japanese Patent Application Laid-Open No. 11-263469 is known.

In this apparatus, one of a plurality of rollers constitutes a control roller whose shaft end is a movable end movable along the belt running direction, and a control roller is provided on the movable end. And a detection ring which is driven to rotate by the transfer conveyance belt displaced to the movable end side. Then, the movable end of the control roller is moved using the torque when the transfer / conveying belt is displaced to the movable end side to rotate the detection ring.

When the movable end of the control roller is moved, the movable end is moved not in the direction perpendicular to the belt running direction but in the front side in the belt running direction. The transfer / transport belt is displaced toward the shaft end opposite to the movable end in the belt width direction.

Therefore, according to this, it is possible to control the belt meandering without using an electric meandering detection circuit or dedicated driving means, and without increasing the belt tension on the movable end side in the belt width direction. Can be.

In the above-described color printer, since the control roller performs meandering control by frictional contact with the transfer / conveying belt, the control roller and the transfer roller are required to properly exert the meandering control function of the control roller. It is necessary to generate a sufficient frictional force between the transfer belt and the transfer belt. For this reason, in the related art, the winding angle of the transfer transfer belt with respect to the control roller is increased.

[0008]

However, in the above-mentioned conventional case, even if the belt wrap angle is secured to a degree considered to be sufficient, for example, if the diameter of the control roller is reduced, a sufficient frictional force is obtained. In order to cope with such a situation, it is necessary to increase the belt wrap angle as much as possible. As a result, the belt layout is excessively restricted, and the entire apparatus becomes large and complicated. There is a problem that is easily caused.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a belt which conveys an object to be conveyed such as recording paper while being guided and supported while being in frictional contact with a control roller. A belt driving device that controls the meandering of the belt by moving the movable end of the control roller to the front side in the belt traveling direction by using the torque of the detecting member that is rotated and driven by the contact with the belt as a driving source; Therefore, the control roller can properly exhibit its meandering control function without being excessively restricted.

[0010]

In order to achieve the above object, according to the present invention, the magnitude of the frictional force between the control roller and the belt ultimately depends on the contact area between the two. By setting the lower limit of the contact area between them, the meandering control function of the control roller can be properly exhibited without receiving excessive restrictions on the belt layout. .

More specifically, according to the first aspect of the present invention, a plurality of rollers arranged so that their axes are substantially parallel to each other,
An endless belt which is wound around the plurality of rollers so as to be able to run, and a span formed between predetermined rollers of the plurality of rollers is a transport span for transporting an object to be transported; And a driving roller for driving the belt to travel to convey an object placed on the belt, and one or more rollers of the plurality of rollers. A control roller having at least one shaft end as a movable end movable along the belt running direction, and contacting the movable end of the control roller with the belt on the control roller displaced toward the movable end. A detection member provided to be driven to rotate;
A belt driving device including a moving unit that moves the movable end of the control roller to the front side in the belt traveling direction by the torque of the detecting member when the detecting member is rotationally driven is premised.

When the coefficient of friction between the control roller and the transfer / transport belt is 0.3 or more, the contact area between the control roller and the transfer / transport belt is 8250 m.
m ² or more.

In the above configuration, the belt of the belt driving device is driven by the driving rollers and travels between the rollers, so that the transported object placed on the belt is moved in the transport span formed between the predetermined rollers. Conveyed.

On the other hand, when the belt is displaced toward the movable end on the control roller with the meandering of the belt, the belt comes into contact with the detection member and rotates the detection member. The moving means moves the movable end of the control roller forward in the belt traveling direction by the torque of the detecting member. Thereby, the control roller guides the belt so as to be displaced to the shaft end side opposite to the movable end in the belt width direction by frictional contact with the belt. Therefore, belt meandering such that the belt on the control roller is displaced toward the movable end is avoided.

When the control roller displaces the belt due to frictional contact with the belt, if the friction coefficient μ between the control roller and the belt satisfies μ ≧ 0.3, the contact area S between the two is reduced. , S ≧ 8250 mm ² , the meandering control function by the control roller can be properly exerted regardless of, for example, the belt winding angle on the control roller and the diameter of the control roller.

When the friction coefficient μ is μ = 0.3, the contact area S is less than 8250 mm ² (S <8250
mm ² ), the control roller does not exhibit a stable meandering control function. When the friction coefficient μ exceeds 0.3 (μ> 0.3), a sufficient frictional force may be ensured even when the contact area S is smaller than 8250 mm ² (S <8250 mm ² ). However, by setting the lower limit value of the contact area S as described above, the restriction on the belt layout is surely eased at least as compared with the conventional case.

According to a second aspect of the present invention, in the first aspect of the present invention, the control roller is constituted by a roller located at one end side of the conveying span in the belt traveling direction among the plurality of rollers.

In the above configuration, since the control roller is located at one end of the transport span in the belt traveling direction, the belt wrap angle with respect to the control roller is shorter than that of the transport span. It is larger than when it is located at one end in the direction. Therefore, the contact area between the control roller and the belt naturally increases.

According to a third aspect of the present invention, in the second aspect of the present invention, the driving roller is constituted by a roller positioned at the front end side of the conveying span in the belt running direction.
The control roller is constituted by a roller located at the rear end side in the belt running direction of the transport span.

In the above configuration, since the driving roller is located at the front end side of the transport span in the belt traveling direction, the drive roller is covered by the belt more than when the driving roller is located at the rear end side of the transport span in the belt traveling direction. The transport operation of the transported object is performed properly. On the other hand, since the control roller is located at the rear end side of the transport span in the belt traveling direction, the contact area with the belt is naturally increased. Therefore, the operation according to the first aspect of the present invention can be properly performed without impairing the proper transport operation of the transported object by the belt driven by the driving roller.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the control roller is provided on the front side in the belt traveling direction.
It is assumed that a roller for separating the control roller from the transport span is provided.

In the above configuration, a roller is located in front of the control roller in the belt traveling direction, and the control roller is separated from the transport span by this roller. Therefore, when the control roller is disposed at one end side in the belt traveling direction of the transport span, fluctuation in the belt thickness direction of the transported object in the transport span due to the meandering control operation of the control roller is avoided. The occurrence of a defect due to the fluctuation is prevented beforehand.

According to a fifth aspect of the present invention, in the electrophotographic apparatus provided with the above-described belt driving device, the transported object is a recording sheet on which a toner image is transferred. And an image forming means disposed along the transport span of the belt driving device and forming the toner image and transferring the formed toner image to a recording sheet on a belt of the belt driving device. And

In the above configuration, in the electrophotographic apparatus,
As the belt of the belt driving device is driven by the driving rollers and travels between the rollers, in the transport span, the toner image is transferred to the recording paper placed on the belt by the image forming means. Therefore, the functions of the inventions of claims 1 to 4 are specifically performed.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows the overall structure of a transfer / transport unit according to an embodiment of the present invention. This transfer / transport unit is incorporated in an electrophotographic color printer to form a toner image. At the same time, it is used to transfer and fix the toner image on the recording paper p.

The transfer / transport unit includes a plurality of (four in the illustrated example) image forming units A to D for transferring the toner images onto the recording paper p while forming the toner images of the respective colors; And a fixing unit E for fixing the toner image transferred to the image forming apparatus. Further, the image forming apparatus has a transfer conveyance belt 1 and drives the transfer conveyance belt 1 in a counterclockwise direction in FIG.
, A belt driving device F that sends the toner image to the fixing unit E via the four image forming units A to D in order.

In each of the image forming units A to D, a cylindrical photosensitive drum 2 for transferring a toner image onto a recording paper p by contact with the recording paper p while forming a toner image, Are transfer rollers 3 for holding the transfer conveyance belt 1 between the transfer rollers and the corresponding photosensitive drum 2 to bring the recording paper p on the transfer conveyance belt 1 into contact with the photosensitive drum 2. And These four image forming units A to D are arranged in order in the belt running direction (the direction indicated by the arrow in FIG. 1) toward the fixing unit E, and the first image forming unit A has a yellow toner. Statue, 2
The third image forming unit B forms a magenta toner image, the third image forming unit C forms a cyan toner image, and the fourth image forming unit D forms a black toner image. The image is transferred onto the sheet p.
In the embodiment, the transfer conveyance belt 1 has a belt width dimension W = 312 mm, and its base material is PET (polyester) or ETFE (ethylene / tetrafluoroethylene copolymer) having a high relative dielectric constant. ), PVDF (vinylidene fluoride resin) or the like, and a dielectric material is disposed on the surface thereof.

As shown in FIG. 2, the belt driving device F includes four rollers 4 to 7 arranged so that their axes are substantially parallel to each other.
Is wrapped around these rollers 4 to 7 so as to run. Among these rollers 4 to 7, the roller 4 disposed near the fixing unit E is a driving roller that drives the transfer conveyance belt 1 to travel by frictional contact with the transfer conveyance belt 1. Transfer unit chassis 8
And is drivingly connected to an electric motor (not shown). As a material of the driving roller 4, a material having a high friction coefficient (μ ≧ 0.3) with the transfer / conveying belt 1, for example, an EPDM (ethylene-propylene-diene copolymer) -based crosslinked rubber is used. Is done. As the other materials for the rollers 5 to 7, metals such as stainless steel and aluminum alloy are used.

A roller 5 disposed on the front side (lower right side in FIGS. 1 and 2) of the drive roller 4 in the belt traveling direction is a tension roller for applying tension to the transfer / conveyance belt 1. The tension roller 5 is rotatably attached to each end of a pair of L-shaped members 9 attached to the chassis 8. Each L-shaped member 9 is pivotally supported by a chassis 8 at a bent portion in a vertical plane perpendicular to the axis of the tension roller 5, and an L-shaped member is provided between the other end and the chassis 8. A tension coil spring 10 that constantly urges the letter-shaped member 9 in the direction in which the tension roller 5 presses the inner peripheral surface of the transfer / transport belt 1 (clockwise direction in FIG. 2) is interposed. A tension is applied to the belt 1.

The roller 6 disposed in front of the tension roller 5 in the belt traveling direction (the right side in FIGS. 1 and 1)
It is a control roller for controlling the meandering of the transfer conveyance belt 1. As will be described later in detail, the control roller 6 has a movable end 6a whose one end is movable in a direction perpendicular to the roller axis, and the movable end 6a moves the transfer conveyance belt 1 to meander. Control.

A roller 7 disposed in front of the control roller 6 in the belt traveling direction (left side in FIGS. 1 and 2) is a guide roller, and a transfer roller formed between the guide roller 7 and the drive roller 4. Of the two upper and lower spans of the transport belt 1, the upper span is the transport span. Also,
Above the guide roller 7, an auxiliary roller 11 rotatable around an axis parallel to the guide roller 7 is arranged. The pair of upper and lower rollers 7 and 11 hold the transfer conveyance belt 1 in a state where the transfer conveyance belt 1 is sandwiched in the belt thickness direction.
, The recording paper p supplied from the paper feeding unit is received on the transfer conveyance belt 1 in accordance with the traveling speed of the transfer conveyance belt 1.

The transfer rollers 3, the guide roller 7, and the auxiliary roller 11 of the three image forming units A to C other than the black image forming unit D among the four image forming units A to D are illustrated in FIG. As shown in FIG. 3, the transfer frame 12 is rotatably held by the transfer frame 12, and the transfer frame 12 is pivotally supported on the chassis 8 so as to be swingable about the same axis as the transfer roller 3 of the image forming section D for black. Have been. At this time, the transfer roller 3 of the black image forming unit D is disposed at a position where the transfer roller 1 is always sandwiched between the transfer roller 3 and the corresponding photosensitive drum 2 and is directly attached to the chassis 8. The transfer frame 12 is moved by a swing mechanism described below in a full-color mode in which full-color printing is performed.
The transfer rollers 3 of all the image forming units A to D
In the monochrome mode in which monochrome printing is performed, the transfer rollers 3 of each of the three image forming units A to C other than the black type are in contact with the photosensitive drum 2. Transfer conveyor belt 1 between
Is pivoted downward from the above-described position for sandwiching.

Below the transfer frame 12, a swing mechanism 13 for swinging the transfer frame 12 according to a mode is provided.
Is provided. The oscillating mechanism 13 has a drive shaft 14 arranged in parallel with the rollers 3 to 7 and 11 described above. The drive shaft 14 is drivingly connected to a driving means (not shown). Each time it is switched, it is driven to rotate by half a turn. A cam member 15 is rotatably connected to the drive shaft 14, and a support shaft 16 disposed parallel to the drive shaft 14 is provided on a side (right side in FIG. 2) of the drive shaft 14. Is provided. The support shaft 16 is supported by the chassis 8 at both ends. An intermediate member 17 and a pressing member 18 are provided on the support shaft 16 so as to extend in a direction orthogonal to the support shaft 16.
It is mounted so that it can swing around. Intermediate member 17
The lower surface of one end (the left end in the figure) has the cam member 1
5, and the pressing member 18 is
The upper surface of one end (the left end in the figure) is arranged to contact the lower surface of the transfer frame 12 from below. The other end portions (both right end portions in the figure) of the intermediate member 17 and the pressing member 18 are disposed so as to face up and down, and a compression coil spring 19 is compressed between these two other end portions. In this case, the intermediate member 17 and the pressing member 18 are constantly urged so that each one end thereof is pressed against the cam member 15 and the transfer frame 12, respectively. And in full color mode,
When the cam member 15 pushes up one end of the intermediate member 17 by the rotation of the drive shaft 14, the other end of the pressing member 18 is pushed down, and one end of the pressing member 18 pushes up the transfer frame 12. At times, the rotation of the drive shaft 14 allows the cam member 15 to allow the one end of the intermediate member 17 to move downward, thereby
Rotates downward.

As shown in FIG. 3, the control roller 6 has a shaft member 20 and is fitted over the shaft member 20.
The roller body 22 is rotatably held on the shaft member 20 via bearings 21 and 21 disposed at both ends in the axial direction. The outer diameter D of the roller body 22 is D = 22 mm. The movable end 6a described above
Is constituted by one end (left side in FIG. 3) of both ends of the shaft member 20. The movable end 6a is
Are supported by support members 23 attached to the chassis 8 by 2, 42,. The other end (right side in the figure) of the shaft member 20 is a fixed end 6b that is immovable in a direction perpendicular to the axis. The fixed end 6b is supported by the chassis 8. In the full-color mode shown in FIG. 6A, the winding angle θ of the transfer conveyance belt 1 with respect to the control roller 6 is 154.95 °.
In the monochrome mode shown in (b), θ = 168.99
° has been made.

The periphery of the support member 23 has a substantially semicircular shape as shown in FIGS.
Reference numeral 3 denotes a transfer / conveying belt 1
It is arranged so as to be located in a direction to receive a force applied to the control roller 6 at a substantially right angle by the tension of the control roller 6. A relatively small first concave portion 24 is formed in a central portion of the linear portion in a notched state, and a relatively small first concave portion 24 is formed on the roller body 22 side (the right side in FIG. 4) of the first concave portion 24. Big second
Is formed in a cut-out state. The movable end 6a of the control roller 6 is connected to the first and second
It is arranged so as to penetrate the recesses 24 and 25 in the axial direction.
At this time, the bottom surface of the first concave portion 24 is in the belt running direction (FIG. 4).
The movable end 6a is guided and supported by the guide surface 23a so as to be slidable in the belt running direction. When the movable end 6a moves forward (upward in each drawing) in the belt running direction, the roller body 22 displaces the transfer conveyance belt 1 toward the fixed end 6b (right side in FIG. 4). When the movable end 6a moves backward (to the lower side in each drawing) in the belt traveling direction, the roller body 22 is transferred to the transfer / transport belt 1 by the guide. The belt 1 rotates while being guided in a direction to displace the belt 1 toward the movable end 6a (the left side in FIG. 4).

A protruding portion 26 protruding laterally in the belt width direction is provided behind the support member 23 in the portion of the chassis 8 (left portion in FIG. 3) to which the support member 23 is attached. Is provided. On the other hand, on the movable end 6 a of the control roller 6, an annular locking member 27 is connected so as to be fitted to the shaft member 20 outside. A tension coil spring 28 is interposed between the projecting ends of the projecting portions 26 and the locking members 27 in an extended state so as to constantly urge the movable end 6a of the control roller 6 rearward in the belt running direction. Accordingly, the transfer conveyance belt 1 on the control roller 6 is biased toward the movable end 6a. That is, in this embodiment, the tension coil spring 28 is attached to the transfer / conveying belt 1 on the control roller 6 by the movable end 6.
It has the function of giving the offset on the a side.

A detecting ring 29 as a detecting member is provided between the roller body 22 of the control roller 6 and the supporting member 23.
Is arranged. The detection ring 29 is rotatably provided on the shaft member 20 of the control roller 6, and a certain axial gap is secured between the detection ring 29 and the roller body 22. The diameter of the detection ring 29 on the roller body 22 side (right side in FIG. 4) is substantially the same as the outer diameter of the roller body 22, and the diameter gradually increases as the distance from the roller body 22 along the axis increases. It is formed in a tapered cross-section, and when the belt side edge portion of the transfer conveyance belt 1 on the control roller 6 comes into contact with the control roller 6 so as to ride up, the rotation is driven in the counterclockwise direction in FIGS. 4 and 5. Has become. The edge of the detection ring 29 on the side opposite to the roller body 22 (left side in the figure) is formed in an outward flange shape protruding radially outward. The side peripheral surface of the tapered portion and the surface of the flange portion on the side of the roller body 22 (right side in the figure) are formed of a material having a required friction coefficient with the transfer / transport belt 1. Examples of such materials include metals such as stainless steel, hard resins such as polyacetal and polyamide, and rubbers mixed with short fibers and made to project short fibers on the surface in a certain direction.

A pinion 30 is disposed on the movable ring 6a of the control roller 6 on the side opposite to the roller body 22 of the detection ring 29 (the left side in FIGS. 3 and 4).
The pinion 30 is connected to the shaft member 20 so as to rotate integrally therewith. On the other hand, a rack 31 that meshes with the pinion 30 is provided at the bottom of the second recess 25 of the support member 23. The pitch line of the rack 31 is set so that the dimension between the pitch line of the rack 31 and the guide surface 23a in the direction perpendicular to the axis of the control roller 6 is constant, that is, the movable end 6
The pinion 30 is set so as to always mesh when a slides on the guide surface 23a. And the control roller 6
When the upper transfer conveyance belt 1 rotationally drives the detection ring 29, the pinion 30 rotates in the same direction as the detection ring 29 and rolls forward on the rack 31 in the belt traveling direction. The movable end 6a moves forward in the belt running direction against the urging force of the extension coil spring 28.

In this embodiment, the contact area S between the control roller 6 and the transfer / transport belt 1 is S ≧ 82.
It is 50 mm ² .

Specifically, the contact area S in the full-color mode is S = 22 × π × (154.95 / 360) × 312 ≒ 9281 [mm ² ]> 8250 [mm ² ]. In the monochrome mode, S = 22 × π × (168.9 / 360) × 312 ≒ 10122 [mm ² ]> 8250 [mm ² ].

In order to secure the contact area S, as described above, the control roller 6 is disposed at the rear end side of the conveying span in the belt running direction. Further, a guide roller 7 is disposed in front of the control roller 6 in the belt traveling direction, as described above, and the control roller 6 is separated from the transport span by the guide roller 7.

Next, a description will be given of the operation of the belt driving device F of the transfer / conveying unit having the above-described configuration during belt meandering control.

Thus, the transfer / transport belt 1 of the printer is driven by the driving roller 4 to travel in the counterclockwise direction between the rollers 3-7. At this time, the movable end 6 of the control roller 6
a moves on the guide surface 23a of the support member 23 rearward in the belt traveling direction by the urging force of the extension coil spring 28,
The transfer conveyance belt 1 is displaced toward the movable end 6a due to frictional contact with the control roller 6 when traveling on the control roller 6. That is, the transfer conveyance belt 1 on the control roller 6
Is shifted toward the movable end 6a.

When the transfer / transport belt 1 is shifted toward the movable end 6 a and the belt side edge contacts the detection ring 29, the detection ring 29 is driven to rotate by the transfer / transport belt 1. Then, the pinion 30 rotates in the same direction as the detection ring 29 and rolls forward on the rack 31 of the support member 23 in the belt traveling direction. As a result, the movable end 6a of the control roller 6 moves forward on the guide surface 23a of the support member 23 in the belt traveling direction against the urging force of the tension coil spring 28. Then, when the transfer conveyance belt 1 travels on the control roller 6, a force in a direction of being displaced toward the fixed end 6 b is applied by friction contact with the control roller 6.

When the transfer belt 1 is displaced toward the fixed end 6b, the transfer belt 1 is separated from the detection ring 29. Thereby, the detection ring 2
Since the rotation of the pinion 9 is stopped, the rotation of the pinion 30 is stopped, and there is no force for moving the movable end 6a of the control roller 6 forward in the belt traveling direction. As a result, the movable end 6a of the control roller 6 is again moved rearward in the belt running direction by the urging force of the tension coil spring 28. As a result, a force biasing toward the movable end 6a again is applied to the transfer conveyance belt 1 on the control roller 6.

Through the repetition of the above-described operations, the transfer / conveyance belt 1 travels at a fixed position on the control roller 6 in the belt width direction. That is, the transfer conveyance belt 1 travels without meandering.

When the control roller 6 displaces the transfer / transport belt 1 toward the fixed end 6b by frictional contact with the transfer / transport belt 1, the friction coefficient μ between the control roller 6 and the transfer / transport belt 1 becomes μ. Since the contact area S between the two 6 and 1 is S ≧ 8250 mm ² under the condition of 0.3, the meandering control function of the control roller 6
This is achieved properly regardless of the belt winding angle θ and the diameter D of the control roller 6.

The control roller 6 is located at the rear end of the transport span in the belt running direction, while the drive roller 4 is located at the forward end of the transport span in the belt running direction. The contact area S of the recording paper p can be easily secured, and the proper conveyance operation of the recording paper p by the transfer conveyance belt 1 driven by the driving roller 4 is not impaired.

Therefore, according to the present embodiment, the plurality of image forming units A to D arranged along the transport span are guided and supported by the driving roller 4 while being brought into frictional contact with the control roller 6 and driven to travel. As a result, when the transfer conveyance belt 1 that conveys the recording paper p is displaced toward the movable end 6a, the torque of the detection ring 29 that is rotationally driven by contact with the transfer conveyance belt 1 is used as a drive source and the control roller 6
Is moved to the front side in the belt traveling direction, whereby the frictional coefficient μ between the control roller 6 and the transfer / transport belt 1 in the transfer / transport unit of the color printer which controls the belt meandering is μ = 0. .3,
Since the contact area S between the two members 6 and 1 is set to be S ≧ 8250 mm ² , the meandering control function of the control roller 6 with respect to the transfer conveyance belt 1 is properly exhibited without being subjected to excessive restrictions on the belt layout. Can be done.

The drive roller 4 is arranged at the front end of the transport span in the belt running direction, while the control roller 6 is arranged at the rear end of the transport span in the belt running direction. 4, the belt winding angle θ on the control roller 1 can be increased without impairing the transport operation of the recording paper p by the transfer transport belt 1 driven by the transfer roller 4, and the contact area S can be easily reduced. Can be secured.

Further, when the control roller 6 is disposed at the rear end side of the transport span in the belt traveling direction, a guide roller 7 is disposed in front of the control roller 6 in the belt traveling direction. 6 is separated from the transport span, so that the control rollers 6
This makes it possible to avoid minute fluctuations of the transfer conveyance belt 1 in the belt thickness direction due to the meandering control operation, and prevent transfer failure to the recording paper p due to such belt fluctuations.

In the above embodiment, only one shaft end of the control roller 6 is set as the movable end 6a.
Both shaft ends may be movable ends.

In the above embodiment, the pinion 30
In the present invention, one end of the wire is wound around the boss portion of the detection ring, and the other end of the wire is fixed to the support member 23 in the present invention. Other means of transportation, such as the above, can be used.

In the above embodiment, the control roller 6
The movable end 6a is biased rearward in the belt running direction by a tension coil spring 28 so that the transfer conveyor belt 1 on the control roller 6 is biased toward the movable end 6a. Means for imparting the deviation is not particularly limited, for example, a roller other than the control roller is arranged to be inclined with respect to the belt width direction.

In the above embodiment, the control roller 6
Although only one of the shaft ends is a movable end, both shaft ends can be movable ends. In that case, the above-mentioned offset imparting means becomes unnecessary.

Further, in the above embodiment, the case of the belt driving device F of the transfer / transport unit incorporated in the electrophotographic color printer has been described, but the present invention can be applied to various belt driving devices. it can.

[0058]

As described above, according to the first aspect of the present invention, the belt which is guided and supported while being in frictional contact with the control roller and conveys the conveyed object is controlled by the torque of the detecting member which is rotationally driven when meandering. In the belt drive in which the movable end of the roller is moved forward in the belt traveling direction to control the belt meandering, when the friction coefficient between the control roller and the belt is 0.3 or more, the contact area between the control roller and the belt is reduced. 825
Since the thickness is set to 0 mm ² or more, the meandering control function of the control roller with respect to the belt can be properly exerted without receiving excessive restrictions on the belt layout.

According to the second aspect of the present invention, since the control roller is constituted by the roller located at one end side of the conveying span in the belt traveling direction, a large contact area between the control roller and the belt is ensured without difficulty. can do.

According to the third aspect of the present invention, the driving roller is constituted by a roller located on the front end side of the transport span in the belt traveling direction, while the control roller is located on the rear end side of the transport span in the belt traveling direction. Since the belt is constituted by rollers that perform the driving, the effect of the second aspect of the present invention can be obtained without impairing the transport operation of the belt driven to run by the driving roller.

According to the fourth aspect of the present invention, the roller is eliminated in front of the control roller in the belt traveling direction, and the control roller is separated from the transport span by the roller. In addition to the above-described effect, it is possible to prevent the occurrence of a trouble caused by the belt fluctuating in the belt thickness direction due to the meandering control operation of the control roller.

According to the fifth aspect of the present invention, since the above-described belt driving device is provided as an electrophotographic apparatus,
The effects of the inventions of claims 1 to 4 can be specifically obtained.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing an overall configuration of a transfer and transport unit according to an embodiment of the present invention.

FIG. 2 is a side view illustrating an overall configuration of a belt driving device of the transfer / conveyance unit.

FIG. 3 is a front view showing a control roller of a belt driving device and a peripheral portion thereof as viewed from a recording paper supply side.

FIG. 4 is a perspective view showing a detection ring of the belt driving device and a peripheral portion thereof.

FIG. 5 is a side view showing a detection ring and a peripheral portion thereof.

FIG. 6 is a side view schematically illustrating a belt winding angle with respect to a control roller in a full color mode (a) and in a monochrome mode (b).

FIG. 7 is a diagram corresponding to FIG. 1 showing an overall configuration of a general transfer / conveyance unit.

[Explanation of symbols]

 F belt driving device 1 transfer / conveying belt (belt) 4 drive roller 5 tension roller (roller) 6 control roller 6a movable end 7 guide roller (roller) 29 detection ring (detection member) 30 pinion (moving means) 31 rack (moving means) ) A to D Image forming unit (image forming means) p Recording paper (conveyed object)

Continued on the front page (72) Inventor Tetsushi Kurokawa 2-229 Sakuragaoka, Higashiyamato-shi, Tokyo Casio Computer Co., Ltd. Tokyo Office (72) Inventor Masayuki Murao 3-2-1-15 Meiwadori, Hyogo-ku, Kobe-shi, Hyogo Prefecture F term in Bando Chemical Co., Ltd. (reference) 2H032 AA05 AA15 BA11 BA18 BA23 3F049 AA02 BB07 BB11 DA04 LA01 LB03 3J103 AA02 AA83 AA85 BA46 CA66 DA03 FA19 FA26 FA30 GA57 GA58

Claims (5)

[Claims] 1. A plurality of rollers arranged so that their axes are substantially parallel to each other, and are wrapped around the plurality of rollers so as to be able to run, and are formed between predetermined rollers among the plurality of rollers. An endless belt whose span is a transport span for transporting the transported object, and one of the plurality of rollers, wherein the belt transports the transported object placed on the belt. A driving roller for driving the vehicle, and at least one of the plurality of rollers,
A control roller having at least one shaft end as a movable end movable along the belt traveling direction, and a rotational drive by contact between the movable end of the control roller and the belt on the control roller displaced toward the movable end; And a moving means for moving the movable end of the control roller forward in the belt running direction by the torque of the detecting member when the detecting member is rotationally driven. A friction coefficient μ between the control roller and the belt, μ
≧ 0.3, and the contact area S between the control roller and the belt is S
≧ 8250 mm ² , wherein the belt drive device is characterized in that ≧ 8250 mm ² . 2. The belt driving device according to claim 1, wherein the control roller is formed by a roller located at one end side of the conveyance span in the belt traveling direction among the plurality of rollers. . 3. The belt driving device according to claim 2, wherein the driving roller is constituted by a roller located at a front end side of the transport span in the belt traveling direction, and a control roller is disposed at a rear end side of the transport span in the belt traveling direction. A belt driving device comprising a roller positioned at the belt driving device. 4. The belt driving device according to claim 1, wherein a roller for isolating the control roller from a conveyance span is disposed in front of the control roller in the belt traveling direction. apparatus. 5. An electrophotographic apparatus provided with the belt driving device according to claim 1, wherein the conveyed object is a recording sheet onto which a toner image is transferred. An electrophotographic apparatus, comprising: an image forming unit that is arranged along a transport span and forms the toner image and transfers the formed toner image to recording paper on a belt of a belt driving device.